PHP File System Functions. Free online PHP and MySQL Web Database Programming Tutorial...

PHP's built-in file system functions could prove to be really powerful tools for every serious PHP web programmer, provided that they are used correctly. We must take extra care when using file system functions.

chmod(), chgrp(), and chown()
All of the above three functions are used to modify the permissions, group and the owner of the argument file or directory. Their syntax follows:

chmod("filename", mode);
chmgrp("filename", newgroup);
chown("filename", newowner);

copy()
We use the copy() function to copy a file. It requires a filename and a destination path in order to copy a file. Its syntax follows:

copy("source file", "destination");

fopen() This function is used to open a specified file for reading or writing or a URL for reading only. Its syntax follows:

fopen("filename", "mode")

The specified mode determines whether the file is opened for reading, writing, or both. The following table lists and describes the values the mode argument can take:

Mode	Description
r	Read-only. The file pointer is at the beginning of the file.
r+	Reading and writing. The file pointer is at the beginning of the file.
w	Write-only. The file pointer is at the beginning of the file, and the file is truncated to zero length. If the file does not exist, attempt to create it.
w+	Reading and writing. The file pointer is at the beginning of the file, and the file is truncated to zero length. If the file does not exist, attempt to create it.
a	Write-only. The file pointer is at the end of the file (it appends content to the file). If the file does not exist, attempt to create it.
a+	Reading and writing. The file pointer is at the end of the file (it appends content to the file). If the file does not exist, attempt to create it.
x	Create and open a file for writing only. The file pointer is at the beginning of the file. This will fail if the file already exists.
x+	Create and open a file for reading and writing. The file pointer is at the beginning of the file. This will fail if the file already exists.

fread()
This function is used to read a specified number of bytes from an open file pointer. Its syntax follows:

fread(filepointer, length);

fputs()
This function is used to write to an open file pointer. Its syntax follows:

fputs(filepointer, content, [length]);

fclose()
We use the fclose() function to close an open file pointer. Its syntax follows:

fclose(filepointer);

mkdir()
This function creates a new directory in the file system. Its syntax follows:

mkdir("pathname", mode);

rename()
This function is used to rename an existing file. Its syntax follows:

rename("oldname", "newname");

rmdir()
This function is used to remove an existing directory form the file system. Its syntax follows:

rmdir("pathname");

unlink()
This function is used to delete a file from the file system. Its syntax follows:

unlink("filename");

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